


Baby Come Back

by casey2y5



Category: Marvel Cinematic Universe
Genre: Age Regression/De-Aging, M/M
Language: English
Status: Completed
Published: 2014-12-19
Updated: 2014-12-19
Packaged: 2018-03-02 04:07:32
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,355
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2798963
Author URL: https://archiveofourown.org/users/casey2y5/pseuds/casey2y5
Summary: <blockquote class="userstuff">
              <p>Tony experimenting with HYDRA tech is stupid. Having other people in the lab while he's doing it is even stupider. On the other hand, Steve is kind of cute like this.</p>
            </blockquote>





	Baby Come Back

**Author's Note:**

  * For [elenajames](https://archiveofourown.org/users/elenajames/gifts).



> I really really really have to love you to write Stony. Fortunately I really really really love Marci.

“Not my fault,” Tony said on autopilot.

“Sir, the only person in the room currently is Captain Rogers.”

“Not the point, J. For the record. Not my fault. He was just standing there and I did not know it was going to do that.”

Tony looked down at the baby sitting in a pile of clothes that had fit perfectly a few moments previously. Steve was watching Tony intently, blue eyes wide with curiosity as he inspected his tiny balled up fist.

“Jarvis, would you mind?”

“Captain Rogers appears to have deaged to approximately ten months old, Sir. No health problems appear imminent, though he is teething. Diapers and other necessary supplies should arrive within the hour.”

“Thank you. Have them sent to Steve’s location when they arrive. I’ll just, uh, fashion something out of the t-shirt until then, yeah.” Tony knew he was rambling, on the verge of a panic attack.

“Sir, I feel it best to inform you Sergeant Barnes is en route to your lab. Would you like me to intercept him?”

“Ah shit. No. I mean its not like I can keep Steve here. Just, uh, give him some warning.”

“Of course.”

Tony glanced at Steve who was sucking his thumb contentedly. He picked up the t-shirt from the floor, spreading it out over one of the work surfaces. He heard the doors slide open and closed his eyes, waiting for the onslaught.

“What happened to him?” Bucky asked.

“Still working that out for myself, actually. One minute I’m talking to Steve then a whir and a snap and I’m trying to figure out how to make a t-shirt diaper- which by the way you wouldn’t happen to know how to do would you? I’m pretty sure I can get him back.”

“Uck! Uck!” Steve screeched.

They both snapped their heads towards him. Chubby arms were waving insistently in the air.

“Yeah, I got you, Stevie,” Bucky said, leaning down to pick him up. “Let’s get you covered up, huh? Bet Stark already has real clothes and everything already ordered for you.”

“Should be here within the hour.”

“Hear that Stevie? You aren’t going to freeze to death.”

Steve cooed happily and Bucky nudged Tony out of the way. Tony watched in awe as Bucky maneuvered the shirt into something resembling a diaper.

“Alright little man, now just try to pee until we get real diapers alright? This thing won’t hold.”

Steve poked at the plating of Bucky’s prosthetic as soon as Bucky picked him back up, obviously entranced.

“How did you-” Tony started.

“Steve was our building's unofficial babysitter, when he wasn’t too sick but couldn’t work. More than one shirt was sacrificed to the cause.”

“Right. Of course.”

“So no idea?” Bucky said, gesturing to the machine in front of them.

“I was waiting for it to cool down so I could get into its guts. I called Steve down to,” Tony hesitated.

“Fuck you over the nearest flat surface? Yeah, I know, Stark.”

“Oh, well yeah. He was standing in front of it and like I said whirr, snap, infant.” Tony paused for a moment letting it sink in. “Shit I broke Captain America. I broke my boyfriend. I don’t which is worse.”

“I told them HYDRA tech was dangerous. That it should be destroyed and forgotten but why listen to the guy who was their prisoner for seventy years right? It’s not your fault Tony- you were just trying to do your job.”

“Right. It still has to cool before I can figure out what it did.”

Bucky shifted Steve weight a bit, trying to keep his body language relaxed.

“Stark, you are going to fix this. Let me make that very clear. Easy there, Steve, that hurts buddy,” Bucky said, immediately getting distracted by pulling Steve’s hand away from the seam of flesh and metal.

“The offer still stands to replace it you know.”

“It works fine. I don’t hate it. You can replace it when it breaks. We may as well go upstairs. You know in case that thing goes off again.”

“Not a bad idea.”

Steve was still preoccupied with the way the plates in Bucky’s arm shifted by the time they got to the common floor. Tony made his way to the counter, pulling a mug down.

“Yeah, you like my arm don’t you? It’s pretty isn’t it?”

Steve babbled loudly in response, slapping his hands forward, smacking Bucky in the chest.

“Coffee, Sarge?”

“What? Yeah, of course.”

Bucky put the baby down on the counter, steadying him with one hand so he could sit on the slippery surface.

“You don’t think he’ll be stuck like this do you? Someone will notice if he goes AWOL,” Bucky pointed out.

“Nah. We’ll get him back to normal. Don’t know the first thing about babies.”

“When he was on tour, before the rescue, you know, he said he was always afraid he was going to squish them, with the new body and all. You should’ve seen his face when he told me. Man had been around babies his whole life and get scared of them after he gets a body that’s not actively trying to kill him.”

“Cap likes kids, huh?” Tony said.

“Yeah. I don’t think he really had any hopes about having them before and after, well, it was hard enough to imagine that the war might end someday, never mind what might happen after.”

Tony set a cup of coffee down, out of Steve’s reach.

“That’s good to know, he said quietly, staring into the depths of his own coffee.

“You ordered toys and stuff too right? Even it’s just today my arm isn’t going to keep him entertained forever.”

“Of course. At least, I think so.”

“You’ve never even thought about kids before have you? And now you’re freaking out?” Bucky said before taking a long drink  of coffee.

“I-”

“He doesn’t care. Well, I mean he does, but he knew what he was getting into with you- what he was giving up. Still chose you.”

“What no ‘I’d have kids with him’? No bitterness?” Tony asked.

“He thought I was dead. So far as he knew I’d been dead for the better part of a century. He moved on. We aren’t the same people we were before the war or even during it. Even if I still felt the same he made his choice and I have to respect that, and we did talk about that, in case he didn’t tell you. He was my friend long before he was anything else.”

“So you really don’t- there’s nothing.”

“No hard feelings, Stark. I mean you hurt him and I’ll end you. He’s still my best friend but nothing is there. Right, Stevie?” Bucky said.

“Uck!”

“Why does he keep saying that?” Tony asked, watching the baby for a minute.

“My name? Probably because I’m in front of him. Sounds the same when he’s stuffed up and delirious.”

“Can’t really picture him sick.”

“Well, good for you.”

Bucky glared at him over his coffee and Tony swallowed hard.

“I wonder if the serum is still active? Do we have a superpowered baby? Which Steve are we going to get back?” Tony asked, not even trying to mask the sudden change in subject.

“Shit, I hadn’t even thought of that.”

“Don’t worry about it yet. We’ll get Bruce, get some blood drawn, figure out what we need to worry about.” Tony said.

“Sorry to interrupt Sir, Sergeant Barnes, but the items you requested are on their way up.”

“Thanks, Jarvis. Would you track Bruce down? Tell him we have a bit of an emergency and could use him.”

“Right away sir. Is Captain Rogers alright?”

“Probably be happier once we get him dressed, but the danger level still appears to be minimal.”

The elevator doors opened, robots carrying in bags and boxes.

“Right so let’s get the little guy dressed,” Tony said, digging through a bag and holding up a Captain America onesie.

Bucky crossed to the living area, Steve in one hand, coffee in the other. He sat down, coffee on the table and Steve on the floor and began coaxing a blanket out of its packaging to lay out. He watched Steve try to pull himself to standing using the coffee table.

“God what did you do? Buy the entire store?”

“Well I didn’t know how long he was going to be like this.”

“You still don’t,” Bucky pointed out.

“So I figured it best to be prepared,” Tony continued, ignoring Bucky’s interjection.

“But this, this is just overwhelming.”

“That is why we have robots. Jarvis has already been compiling a list of nannies should this become a long-term situation.”

“You’d leave him with a nanny?”

“Of course. We have to go Avenging and what not.”

“I’ll take care of him. Put him with a nanny- honestly, if there’s a threat to the city or something then we get a sitter.”

“I was raised by nannies. I turned out fine.”

Bucky spared him a look of contempt before prying open a box of diapers.

“Well maybe not fine, but I’m functional. Why are we even arguing about parenting options?”

“Because we’re as good as. I mean, I am the one who makes the calls if he’s incapacitated, if you’ll recall from those stupid will things Pepper made us do, and this is pretty incapacitated.”

“So you’ll, what, take him away and get a job as a short-order cook if we disagree. Say you’re his dad if he grows up and doesn’t remember. You won’t blend in for long,” Tony said, gesturing to the arm.

Bucky grabbed Steve, laying him down on the blanket, starting the process of changing a wiggly baby.

“I’m not threatening to take him away, Tony. Besides I was a damn good short order cook. Just saying if you’re going to do anything drastic I’m the one with the right to stop you and I would. I’d rather change his diapers than lose him for real.”

He finished taping the diaper shut, sparing a moment to tickle Steve’s belly, earning a delighted squeal before snatching the jumper out of Tony’s stunned hand. He pulled Steve’s arms through, talking to the baby, explaining what he was doing and carefully snapping shut the legs.

“Uck! Uck!” was followed by more babbling.

“Yeah, you’re telling me buddy. Probably a good thing you don’t understand right now huh? You wanna sit up?” Bucky asked, letting Steve grab onto his fingers and helping him pull himself to sitting.

“You’re really good at the whole baby thing.”

“I like kids. Besides you hadn’t even picked him up out of his clothes when I got there so I just sort of figured it was on me.”

“Don’t know how,” Tony muttered.

“What was that?”

“I don’t know how to hold a baby. There’s the soft spot.” Tony gestured to his own head. “And supporting their necks and I figured I’d probably kill him if I tried.”

“Jarvis said he was ten months old, give or take, when he told me what happened. He’s sitting up fine. You aren’t going to kill him if you pick him up.”

Steve was chewing eagerly on his fist, drool managing to drip down his chin already. Bucky reached out with the hem of his t-shirt to wipe his face dry. Tony regarded them both.

“Right. Easy as pie.”

“I won’t let you hurt him. One hand on his side under his arm, the other under his butt. He probably needs to be fed or at least a bottle so pay attention to him while I get it ready. Maybe find something for him to chew on in this mess in the mean time.”

Tony crouched down next to them. Steve was watching him, wide blue eyes tracking his every movement.

“Alright buddy I’m going to pick you up now so try not to scream or anything. Bucky is going to make you some lunch since we don’t know when you ate last or if you’re still all super-soldiery.”

Bucky watched them out of the corner of his eye when he got up, reasonably confident Tony wouldn’t actually manage to break Steve, but erring on the side of caution. Most of his attention was focused on digging through the boxes to find bottles and formula. Tony soon had Steve well in hand, bouncing the baby gently. Steve, for his part, was apparently delighted by the new textures Tony’s face provided.

“Yeah, yeah, you and the goatee Steve,” Tony laughed.

“Didn’t need to know,” Bucky said.

“You probably already did know that,” Tony said, waggling his eyebrows.

“Not the point. No innuendos around the baby.”

Tony humphed before grabbing a stuffed toy and tearing the tags off with his teeth. He made it do a little dance in front of Steve’s face and Steve grabbed for it. Tony relinquished the toy and made a face when Steve stuffed it in his mouth.

“That’s not really food. Barnes how’s the bottle coming? Steve here is rebelling by eating his toys.”

“Babies put things in their mouth. Something about exploring their environment is what they’re saying now. And a few more minutes.”

“You’re not gonna have to chew on that much longer, kid.”

“Steve is like fifty years older than you.”

“So he’s a baby right now. Besides I’m older than both of you were when you uh didn’t die.”

Bucky snorted and checked the temperature of the bottle, apparently deeming it satisfactory.

“Tony, wrist. So you know what it feels like.”

Tony held out his wrist obediently, letting Bucky drip a few drops of warm formula onto him. Bucky grinned at him before handing off the bottle and turning to deal with the pot he had used to heat the bottle up.

“Right. This should be easy.”

He maneuvered the baby to a better position before tentatively offering the bottle. He coaxed into Steve’s mouth as the elevator dinged. Tony glanced up to see Bruce come in before turning his attention back to the baby. Steve reached up to grab onto the bottle.

“He’s not strong enough to hold it up by himself,” Bucky said without turning around. “Hey, Bruce.”

“I assume Tony feeding a baby was the cause for alarm,” Bruce said, watching intently.

“It’s more that the baby is Steve,” Tony said.”

“What did you do?”

“The HYDRA tech they had me working on. Steve came down and the thing just sort of went off when he was standing in front of it. Jarvis?”

“Yes, sir?”

“When you contact people about this please explain the situation. I’m getting bored repeating myself.”

“Yes, sir.”

“And you called me because?”

“Just need to know if he’s still super-soldiery or if we’re going to get skinny Steve back when we turn him back into an adult.”

“You mean you need to know the damage you did.”

“Tony!” Bucky said, spinning around. “Pay attention or he’s going to start sucking down air.”

Tony blinked, looking down, surprised to see the bottle mostly empty.

             "Sorry Steve, " Tony said automatically, putting the bottle on the counter.

             "Do you have any idea how old he is? "

              " Jarvis said ten months so that's what we're going with."

Tony pulled Steve up onto his shoulder, patting his back gently, trying to ignore Bruce's eyes on him. He heard a tiny burp before warm liquid gushed over his shoulder.

"Aww, Steve I liked this shirt."

Bucky laughed and Tony turned to glare at him. He held his hands out for the baby who Tony gladly handed over.  Steve laughed as soon as he was in Bucky’s arms.

"Yeah spitting up on Tony is funny isn't it? Go change. I'll bring Bruce up to speed."

Bucky chuckled at Tony’s retreating back before turning to Bruce. He eyed the other man warily, not having spent enough time with him to trust him, especially not with Steve so vulnerable.  Still he indicated the couch and settled himself on it, Steve sitting on his lap.

"So what happened? " Bruce asked, still looking at the baby like he expected this to be an elaborate prank.

"According to Tony, Steve was in the wrong place when it went whirr click then a baby.  HYDRA tech they had him reverse engineering or some shit."

Bruce was nodding. Steve shifted, reaching for Bucky’s arm.

"Yeah, Stevie I got you," Bucky told him. Steve’s face screwed up, nose crinkling. "Really Stevie? Okay then, well let me know when you're done."

"Well, Tony’s the brain you want for the tech but I'll need to draw some blood to make sure the serum is still active. “

"That's why we called.  He looks healthy though. "

"He does. Bring him down to the lab when you're ready. "

*****

Bucky had eyed the sling warily at first, thinking Steve was too old to enjoy it. Then he had started crying when Bruce drew blood and hadn’t stopped. It turned out direct contact calmed him right down which is how Bucky found himself walking around shirtless, a baby strapped to his front, working on making dinner. Steve was out cold against him, soft breaths puffing out.

“Jarvis, do we have any good paprika left?”

“It should be in the cabinet to your right, Sergeant Barnes. Also, Dr. Banner has asked me to inform you that he has the results from Captain Rogers’ blood draw and would like you to come down at your earliest convenience.”

“Thanks. Tell him we’ll be down as soon as this simmers.”

“Captain Rogers has calmed down I take it?”

“Yeah. Sleeping like a baby,” Bucky said.

“And you’re all right, Sergeant Barnes?”

“Yeah. I mean I feel a bit like a housewife with a baby attached to me and making dinner but I’ll be okay as long as Steve is okay.”

Bucky dumped the spices into the pot, giving the stew a final stir before heading down to the lab. Tony was in his own, fiddling away with the tech, determined to figure out a way to reverse it. He supported Steve absently on the way down, not trusting the sling entirely. Steve shifted to a more comfortable position, kicking out. As soon as he was within sight of Bruce he put his finger to his lips and pointed at the baby.

“I just got him down about twenty minutes ago,” he whispered.

“Of course. It seems like the serum is still in effect.”

“Ah that explains it.”

“Explains what?” Bruce asked, looking alarmed.

“Oh, he kicked me on the way down and I felt it. Would make sense.”

“He’s fine though. Whatever it did, it didn’t seem to have any negative effects beyond turning him into a baby.”

“That’s good. Not the being a baby part, but that he’s healthy.”

‘You’re good with him,” Bruce noted. “Better than Tony, at least.”

Bucky shrugged. “Is there anything else? I have dinner on. I’ll bring some down for you when its done, if you want.”

“I’ll be up in a few minutes, if that’s alright.”

“Course. Could always use company.”

*****

Bucky had checked the crib the robots had assembled twice before putting Steve in it the first night before turning the baby monitor on. When Steve woke up at exactly six, he had cursed before getting them both ready for the day. By day three they had settled into a comfortable routine. Steve generally wasn’t too fussy, unless the pain of his cutting teeth was too bad, but Bucky learned the numbing gel was the easiest way to take care of that. There was also a lot of pestering Tony until Jarvis told them they were banned from the lab until further notice.

“Stevie,” Bucky said, coaxing the baby to look at him again, before hiding behind his hands. “Stevie, peek-a-boo.”

Steve squealed in delight, bringing his hands together. Bucky did it again, ignoring the sound of the elevator doors opening.

“Well, James, they’re hardly shaking in their boots now. Banner wasn’t kidding.” Bucky looked up, not as surprised as he should have been to see Natasha leaning against the counter, combat gear still on.

“Uck?”

“He says your name too?”

“Apparently it’s all he says,” Bucky said, picking Steve up and wandering across the room.

“How close is Stark to figuring it out?”

“Not close enough. He’s probably going to work himself to death figuring it out.”

Steve was staring at Natasha until she looked at him directly, at which point he hid his face in Bucky’s chest.

“He’s shy,” she said.

“Just hasn’t met you yet. Pepper stopped by yesterday and he did the same thing.”

“Bruce said you’re taking care of him.”

“Well, just feels right. I mean someone has to. I’m surprised no one has noticed Steve’s missing yet.”

“Well, it’s not like he leaves the Tower much anyway.”

“Still, Tony needs to hurry up before something happens and people really do notice.”

“He’s doing the best he can, I’m sure. He wants Steve back just as much as you do.”

Steve turned his head to regard Natasha warily. He reached up to touch Bucky’s face.

“What is it, Stevie? You want to see Tasha better huh?” Bucky maneuvered the baby so that they were back to chest and Steve could see the world around him a little easier. He wriggled in Bucky’s grasp reaching out.

“He’s sorta cute like this. I mean it’d probably be better if he was potty trained and could talk but still for a baby he’s not bad.”

“So you’ll watch him while I shower later?”

Steve leaned forward more, arms waving.

“He’s going to fall,” Natasha said.

“No he’s not. He wants you to hold him, but I’m assuming you’re covered in blood.”

“I’m perfectly clean. Just haven’t gotten out of this yet or do you not want me to hold him. I can say I’m covered in blood in that case.”

Bucky passed the baby off and turned around, moving a path to the floor through the mass of things that seemed to have accumulated in their living room. By the time he had eyes on them again Natasha was making faces and Steve was squealing with laughter.

“Yeah, Natalia is funny when she wants to be isn’t she, Stevie?”

Natasha looked at him like she had forgotten he was in the room and quickly shifted the baby to her hip. Steve looked surprised by the sudden movement but settled back down quickly, finding the tab of a zipper.

“No. No. I wouldn’t pull on that,” she said, disengaging his hand.

“What’s in the pocket?” Bucky asked.

“Not a pocket. Don’t want to be half naked in your living room.”

Bucky roared with laughter. “Go change. Give him here.”

“Welcome back, Agent Romanoff. Sergeant Barnes, Sir has requested your presence in the lab, along with Captain Rogers.”

“Thanks Jarvis, we’re headed down now.”

“May I suggest you bring some of Captain Rogers’ clothes that would fit him as an adult.”

Bucky grinned. Natasha nodded indicating she’d watch Steve for the moment while Bucky went to grab a t-shirt and pair of jeans. As soon as the clothes were in hand he was scooping Steve into his arms and striding to the elevator. Natasha followed, pushing the button for her own floor.

“Good luck, James. I hope Tony’s managed to fix it.”

“You and me both.”

Bucky hurried down the hall to Tony’s lab, talking to Steve the whole way. He was more surprised than he should have been to see the lab in shambles, cups of coffee strewn everywhere and an exhausted Tony pacing in the middle of it.

“Have you slept at all?” Bucky asked.

“Passed out for a couple hours around hour fifty.”

“Right. Of course. Did you manage to-”

“I think, think I managed to reverse the technology so it can do its thing again. Even managed to figure out the on button.”

“Oh, well that’s a relief. I thought it wasn’t on when it turned Steve into a baby.”

“It wasn’t. It shorted out.”

“And it’s safe?” Bucky asked, pulling Steve closer to him automatically.

“Safe is a relative term. It’s probably not going to kill him and the best I can tell it will turn him back into an adult. There’s always the off chance we’ll have Hulk 2 on hand but-”

“It’s as safe as it can be, given the circumstances and what it is.”

“Yes. I wouldn’t have called you down otherwise. So put him in front of there- he won’t crawl away will he?”

“He’ll stay put,” Bucky said. “Okay, Stevie gonna put you down and hopefully we’re gonna get grown-up you back. I mean you’re great and all but we kind of miss you being potty trained.”

“Least he didn’t try to jump out of any planes.”

“Yeah, just the couch,” Bucky snorted, putting Steve down in front of the machine.

Steve watched Bucky backup to stand next to Tony and his lower lip trembled. Bucky took the glasses Tony held out.

“None of that now, Stevie. Gonna be just fine.”

“You ready Barnes?”

“Not at all.”

Tony pushed the on button, the machine whirring loudly. Bucky screwed his eyes shut, not willing to watch. He cracked an eye open at the click and breathed a sigh of relief when Steve was standing there, hands over his junk, looking confused.

“Welcome to the future,” Tony said.

Steve glanced around, panic crossing his face.

“It’s been three days, Steve. Stark turned you into a baby,” Bucky clarified, handing over the clothes

“Oh, I, I don’t really remember much. I’m never coming down here again,” Steve added.

Tony snorted. “Right.”

There was a beat while Steve got his pants on before Tony was launching himself across the room, arms wrapped around Steve, kissing his shoulder and apologizing profusely. Bucky glanced around, before deciding it was high time to beat a hasty retreat. Besides there was an entire nursery that needed to be taken down.

“Bucky,” Steve stopped him before he got through the doors, one arm wrapped around Tony’s waist. “Thanks.”

“Anytime, Stevie.”


End file.
